The urban informal development is undeniable reality of a great number of cities across the world. Hence, many urbanism studies have been devoted to this topic. These scholarships have used various theoretical frameworks to explain this phenomenon. However, no comprehensive theoretical base is available for the subject yet. Therefore, this study aims to formulate an alternative theoretical foundation relying on contextualist worldview capacities. The research has been conducted with descriptive-analytical methodology through the review of contextualist literature. The results of the study in the first step answer the questions about the origin, philosophical background, evolution process, approaches, and dimensions of contextualism. In the next step, the research developed a new reading of contextualism to be a suitable theoretical framework for informal urbanism studies. This reading explains informal urbanism relying on multiple ontologies, pragmatic and plural epistemology, mixed methodology, and inclusive-flexible analytical framework. In the theoretical dimension, the results have revealed the reductionism of the view promoting contextualism in urbanism, so have reformulated and customized it to explain informal development. In the scientific dimension, moreover, it proposed the reading of suitable policymaking for urban managers regarding the informal settlements. Such a platform is based on accepting contextual (local) realities and avoiding the mostly negative metanarratives. Manuscript profile